Merge pull request #1200 from Unity-Technologies/macos-fat32-empty-file-new-mono

Handle the empty file inode on macOS and FAT32

Author: Joshua Peterson

mono/metadata/w32file-unix.c

@@ -1791,6 +1791,22 @@ static mode_t convert_perms(guint32 sharemode)
 }
 #endif
 
+static gboolean already_shared(gboolean file_alread_shared, ino_t inode)
+{
+#if PLATFORM_MACOSX
+	/* On macOS and FAT32 partitions, we will sometimes get this inode value
+	 * for more than one file. It means the file is empty (FILENO_EMPTY is
+	 * defined in an internal header).  When this happens, the hash table of
+	 * file shares becomes corrupt, since more then one file has the same
+	 * inode. Instead, let's assume it is always fine to share empty files.
+	 * (Unity case 950616).
+	 */
+	return file_alread_shared && inode != 999999999;
+#else
+	return file_alread_shared;
+#endif
+}
+
 static gboolean share_allows_open (struct stat *statbuf, guint32 sharemode,
 				   guint32 fileaccess,
 				   FileShare **share_info)
@@ -1800,7 +1816,7 @@ static gboolean share_allows_open (struct stat *statbuf, guint32 sharemode,
 
 	file_already_shared = file_share_get (statbuf->st_dev, statbuf->st_ino, sharemode, fileaccess, &file_existing_share, &file_existing_access, share_info);
 
-	if (file_already_shared) {
+	if (already_shared (file_already_shared, statbuf->st_ino)) {
 		/* The reference to this share info was incremented
 		 * when we looked it up, so be careful to put it back
 		 * if we conclude we can't use this file.